Generally speaking, I like the idea of a recurring fee. As for now or at least as long as Nostr is growing quickly, a one-time-fee should be sufficient. Newer nostriches will pay for the early innovators, I am fine with that. However, in the long run a recurring fee will be needed.
But I think as a customer I would prefer top-ups, as long as there are no lightning-only recurring payments without a 3rd party.
What are your plans #[2] about recurring payments? I have seen in the nostream database that there is a balance field, I suppose it is planned to be used for a recurring payment, isn't it?